Rudder Stock Failure Leading To Yacht Sinking

[redbopeep]

Originally Posted by Trim50

Also, if I'm not mistaken, the rudder on the Hanse is not supported from the bottom of the shaft thus loading the rudder post in bending by virtue of design. Why then would they place a diameter reduction high up on the shaft where the bending moment from the rudder is maximum? The bending moment from the hydraulic ram would pale by comparison simply due to the length of the rudder moment arm and the relative location of the tiller arm.

http://hanseyachtsflorida.com/Photos/400/4...er_WEB_GB_C.pdf

Its supported at some point in that "tube" there's a bearing surface. Gotta be. Else, really, really bad design.

Expectation is that only unsupported area exists outside of hull just on top of the blade.

[redbopeep]

Loading of hydraulic ram is localized, equal and opposite the rudder loading which is spread, by this point, through the full stock diameter. Strain is very high locally with the autopilot hydraulic ram asymmetry. Quick crack growth. No diversion path for stresses locally applied like that.

[Trim50]

Originally Posted by redbopeep

Onwards, Trim, I hope you have a good inspection schedule of your autopilot and rudder stock? What are your plans regarding this?

I have a full keel vessel with a barndoor rudder supported from top and bottom on a 2.25" diameter stainless steel post thru-hull above water and two keyways on my bronze tiller arm. My weakest link is the ram mounting to the tiller arm from below as described above.

Also, inspection is difficult since I shoe-horned a genset in below the cockpit in front of the steerage. I'm sure I will eventually regret installing it there simply due to maintainance of the genset alone. I do plan to buy loads on solar, so the genset will be backup power only.

[Trim50]

Originally Posted by redbopeep

Its supported at some point in that "tube" there's a bearing surface. Gotta be. Else, really, really bad design.

Expectation is that only unsupported area exists outside of hull just on top of the blade.

Yep...most likely, but it would have to be one hellova bearing design not to transfer any bending load to the upper bearing.

I'm like'n my full keel barndoor rudder more all the time.

[redbopeep]

speaking of barn doors...John, who's working with my hubby, Dave, on the boat is calling our rudder the "Snoopy" rudder because he thinks its going to look like snoopy riding his doghouse and shooting at the Red Baron

Its huge with trailing edge sticking way back there. Keel hung, of course. Thanks for the compliment on our blog regarding the gudgeon casting. Its (gudgeon) installed now, but no pics on the site yet. the rudder is about 2.25" thick on the trailing edge with a bronze strap around its trailing edge. John wanted to feather it down and we had a big discussion about how I wanted turbulence at the trailing edge to help with the turn. He just said that my Snoopy rudder has plenty of beef to turn the boat with out extra turbulence...

[Bakethrough]

Its always really sad when a nice boat goes to the bottom of the sea. Sadly often it is because of lousy work... Big companies nowadays are using a lot of subcontractors so things on these pictures are no exception. Its just sad where industry is going.

[freddie12345]

Thanks for sharing this. Very interesting.

http://www.sailinglatest.com/news

[SeaCure]

Says in the ZF SeaDrive manual under coatings and paint to NOT paint the drive with copper or zinc based paint in case you missed the metal class. The quadrant is cast aluminum and the shaft is a stainless pipe on the Hanse I looked at. It was also in a well which did not drain into the hull.
The quadrant corrosion with aluminum and stainless can be cleaned up with diluted drain cleaner. Folks tend to hammer at them or put penetrating oil and heat none of which break the oxidized aluminum.
A solid aluminum shaft would be silly heavy and I can’t see it breaking other than at the quadrant. It does sound like it’s from fudging an auto helm arm. They may have caused the bearing to move upwards. Pushed up inside it could tear the boat open.

[Brent Swain]

The fig leaf, cantilevered spade rudder has the highest failure rate of any rudder design ,being only cantilevered off one end. Structurally unfit for long term offshore cruising. It also makes a self steering wind vane, exponentially more complex, expensive, and vulnerable. A good solid skeg eliminates this problem, and makes a rudder vastly stronger. I have hit rocks at hull speed with my skeg,*with zero damage. My outboard rudder eliminates so many problems . I can see everything on it from my deck . My outboard rudder head is exponentially stronger than a rudder shaft.